The present invention relates to an ink fountain apparatus for a printing press which causes an ink in an ink fountain to flow out continuously by a predetermined amount.
An inking arrangement for supplying a printing ink to a plate mounted on the plate cylinder of an offset rotary press comprises an ink fountain apparatus for causing the ink stored in its ink fountain to flow out by a predetermined amount, and a large number of rollers for transferring the flowed ink while smoothing it in respective directions, thus supplying the ink to the plate surface. FIG. 3 shows the arrangement of the above conventional ink fountain apparatus. More specifically, referring to FIG. 3, an ink fountain roller 1 is rotated in a direction indicated by an arrow. Stays 2 and 3 each having almost the same length as that of the ink fountain roller 1 are disposed obliquely below the ink fountain roller 1, and a blade table 4 having the same length as that of the ink fountain roller 1 is mounted on the stay 2 by bolts 5. An ink blade 6 constituted by a thin stainless steel plate and having the same length as that of the ink fountain roller 1 is mounted on the blade table 4 by screws such that its distal end is very close to the cylinder surface of the ink fountain roller 1. Triangular ink embankments 7 are provided at two end portions of the ink blade 6. An L-shaped adjustment piece 8 is pivotally mounted on the other stay 3, and an adjustment screw 9 is screwed in the adjustment piece 8. An ink 10 is stored in the ink fountain defined by the ink fountain roller 1, the ink blade 6, and the two ink embankments 7. As the ink fountain roller 1 is rotated, the ink 10 flows out through the gap between the ink fountain roller 1 and the ink blade 6 to form an ink film on the surface of the ink fountain roller 1. The ink film thickness, i.e., the amount of ink to be supplied to the plate is adjusted by manually rotating the adjustment screw 9 forward or backward to elastically deform the ink blade through the adjustment piece 8, thus adjusting the gap between the distal end of the ink blade 6 and the circumferential surface of the ink fountain roller 1.
The printing speed of the offset printing press has been increased recently. Accordingly, a variation occurs in ink transfer due to the thermal deformation of a rubber roller that generates heat under a high-speed operation. Also, since an ink ductor generates heat as it performs reciprocal rotating movement with quick deceleration and quick acceleration, the ink fountain roller contacting the ink ductor is thermally deformed. As a result, the thickness of the ink film varies to decrease the printing density.
In order to solve this problem, Japanese Patent Laid-Open Nos. 59-41269 and 2-184439 propose a technique to set constant the thickness of the ink film.
Referring to FIG. 3, the ink fountain apparatus for a printing press proposed in these gazettes further comprises an adjustment roller or rod for contacting the circumferential surface of the ink fountain roller or the bearing bush of the ink fountain roller. Thermal deformation of the ink fountain roller or the bearing bush of the ink fountain roller is extracted through the adjustment roller or rod, and the ink fountain is rotated about a support shaft 11 shown in FIG. 3 on the basis of the extracted change component corresponding to the deformation, thus maintaining the gap between the circumferential surface of the ink fountain roller and the ink blade at a constant value.
In the conventional ink fountain apparatus for the printing press described above, however, as the deformation of the ink fountain roller is temporarily converted to a rotational moving amount of the ink fountain and then to the linear moving amount of the ink blade, the deformation amount of the ink fountain roller and the moving amount of the ink blade with respect to the circumferential surface of the ink fountain roller do not precisely coincide with each other. Hence, it is difficult to maintain the gap between the circumferential surface of the ink fountain roller and the ink blade at a constant value.